Structure-property relationships in polyolefins [Elektronische Ressource] / vorgelegt von Cristian Eugen Hedesiu

513959

Sujets

• Physik

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2007
• Nombre de lectures: 8
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

Structure – Property Relationships in
Polyolefins










Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der Rheinisch-
Westfälischen Technischen Hochschule Aachen zur Erlangung des akademischen Grades
eines Doktors der Naturwissenschaften genehmigte Dissertation



vorgelegt von

M. Sc. Cristian Eugen Hedesiu

aus Iclod, Romania





Berichter: Universitätsprofessor Dr. Dr. h.c. Bernhard Blümich
Universitätsprofessor Dr. -Ing. Edmund Haberstroh



Tag der mündlichen Prüfung: 12 December 2007
Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar.
Contents

Contents

1 INTRODUCTION AND MOTIVATION 1
2 POLYETHYLENE AND POLYPROPYLENE MORPHOLOGY 5
2.1 Polyethylene 5
2.1.1 History 5
2.1.2 Properties and economic relevance 5
2.1.3 Morphology of polyethylene 5
2.2 Polypropylene 7
2.2.1 History 7
2.2.2 Properties and economic relevance 8
2.2.3 Morphology of isotactic polypropylene 8

3 EXPERIMENTAL METHODS 13
3.1 Introduction 13
3.2 Transmission electron microscopy 13
3.3 Scanning mi
3.4 Atomic force microscopy 14
3.5 Differential scanning calorimetry 14
3.6 Small-angle X-ray scattering
3.7 Wide angle diffraction 15
3.8 Infrared spectroscopy 15
3.9 Mechanical tests 16
3.10 Nuclear magnetic resonance 17
3.10.1 Proton wide-line NMR spectroscopy 17
3.10.2 transverse magnetization relaxation 18
3.10.3 Spin-diffusion NMR experiments with dipolar filters 19

4 HIGH DENSITY POLYETHYLENE 27
4.1 Introduction and motivation 27
4.2 Materials 30
4.3 Morphology of HDPE by TEM 30
4.4 Crystallinity and morphology by SAXS 31 Contents

4.5 Temperature dependence of the phase composition and chain mobilities
of HDPE by NMR 32
4.6 The effect of annealing on chain mobility and the phase composition by
NMR 35
4.7 The thickness of domains in HDPE 36
4.8 The effect of annealing on the thickness of domains and chain mobility 39
4.9 Conclusions 40

5 ISOTACTIC POLYPROPYLENE 43
5.1 Introduction and motivation 43
5.2 Materials 44
5.3 Crystallinity by DSC 44
5.4 Morphology of iPP by TEM 47
5.5 Crystallinity and Morphology by SAXS 48
5.6 Solid-state NMR study of phase composition, chain mobility, and domain
thicknes 51
5.6.1 Temperature dependence of phase composition and chain mobility 51
5.6.2 The effect of annealing temperature and annealing time on the
phase composition and chain mobility 53
5.6.3 Comparison of the amounts of the rigid fraction/crystallinity
obtained by NMR, SAXS, and DSC 55
5.6.4 Comparison of the domain thicknesses measured by DQ and
Goldman-Shen dipolar filters in spin-diffusion experiments 55
5.6.5 Temperature dependence of the domain thickness 57
5.6.6 The effect of annealing temperature and annealing time on the
domain thickness of iPP sample 58
5.6.7 Thickening of crystalline domains during annealing 59
15.6.8 Correlation between the H transverse magnetization rate and
the domain thickness of the crystalline domains 61
5.7 Conclusions 63

6 AGING ON ISOTACTIC POLYPROPYLENE 65
6.1 Introduction and motivation 65
6.2 Materials 66 Contents

6.3 NMR data processing 67
6.4 Mechanical results
6.5 X-ray results 69
6.6 DSC
6.7 Changes induced by aging at 28° C in the phase composition and chain
mobility of homopolymeric iPP samples 73
6.8 Changes induced by aging at 70-130° C in the phase composition and
chain mobility of homopolymeric iPP samples 75
6.9 Discussion: physical ageing in homopolymeric iPP samples by NMR
and mechanical analysis 79
6.10 Conclusions 80

7 UNIAXIALLY DEFORMED ISOTACTIC POLYPROPYLENE 83
7.1 Introduction and motivation 83
7.2 Materials 85
7.3 Stress-strain characteristics 85
7.4 Crystallinity by IR 86
7.5 Phase content and chain mobility by NMR at 70° C 87
7.6 Effect of drawing ratio on the phase composition and chain mobility 89
7.7 Effect of drawing rate on the phase comobility 90
7.8 Effect of drawing temperature on the phase composition and chain
mobility 91
7.9 Effect of draw ratio and drawing temperature on the domain sizes of iPP 93
7.10 Correlation between the amount of the rigid fraction and the thickness of
the rigid domains 95
7.11 Correlation between the long period and the drawing temperatures 96
7.12 Correlation between the H transverse relaxation rate and the domain
thickness of the rigid domains 98
7.13 Conclusions 99

8 IMPACT MODIFIED ISOTACTIC POLYPROPYLENE 103
8.1 Introduction and motivation 103
8.2 Materials 104
8.3 Morphology by TEM and AFM 105 Contents

8.4 Crystallization temperature and heat of fusion by DSC 108
8.5 Tensile and flexural tests 109
8.6 Phase content and chain mobility by NMR at 70° C 111
8.7 Aging in impact modified PP copolymer at 70 ° C by NMR 112
8.8 obility by NMR at 0° C 114
8.9 Conclusions 118

9 GENERAL CONCLUSIONS 119

REFERENCES 123































Abbreviations and Symbols


Abbreviations and Symbols

NMR nuclear magnetic resonance
AFM atomic force microscopy
a, b, c dimensions of unit cell
c heat capacity p
C , C WLF coefficients 1 2
CLTE coefficient of linear thermal expansion
d thickness of the amorphous fraction a
d thickness of the intermediate fraction i
d , d thickness of the rigid fraction r c
DSC differential scanning calorimetry
D diffusion coefficient amorphous fraction a
D diffusion coefficient intermediate fraction i
D diffusion coefficient rigid fraction r
DQ double quantum
FID free induction decay
GS Goldman – Shen filter
H enthalpy
HDPE high density polyethylene
HEPS Hahn echo pulse sequence
LDPE low density polyethylene
I scattering intensity
ICP impact copolymer
IR infrared spectroscopy
L long period p
LLDPE linear low density polyethylene
M second van Vleck moment 2
M number averaged molar mass n
M weight averaged molar mass w
PE polyethylene
PP isotactic polypropylene
q scattering vector Abbreviations and Symbols

SAXS small angle X-ray scattering
SEM scanning electron microscopy
SEPS solid echo pulse sequence
SPE single pulse excitation
t aging time a
tmixing time d
T longitudinal relaxation time 1
T transverse relaxation time 2
T glass transition temperature g
0T equilibrium melting point m
TEM transmission electron microscopy
XRD X-ray diffraction
W crystallinity by DSC
WAXD wide angle X-ray diffraction
WAXS wide angle X-ray scattering
WLF William – Landel – Ferry equation
wt% weight percent
Δν full line width at half height 1/2
ρ proton density
γcorrelation function
λ draw ratio Chapter 1. Introduction and Motivation
Chapter 1

Introduction and Motivation

The extensive and still increasing usage of polymeric materials stems from their unique
physical and mechanical properties. Combined with economic advantages in terms of price
and market availability polymeric materials became a logical choice for a wide range of
applications. For many purposes, their performance is much better than that of conventional
materials such as metals, ceramics or wood. Among the polymeric materials, polyolefins hold
an important role, becoming more and more an indispensable part of our daily life. We can
identify so many products around us ranging from our basic necessities such as tooth brushes,
clothing, storage bottles, and carry bags to special applications like gas and water pipelines,
automotive applications, and biomedical implants all made from polyolefins.
The macroscopic properties of polyolefin materials are not only determined by the size
and construction of the application but to a great extend also to the morphology of the
polyolefin used. Polyolefins show a very complex morphology in which various levels of
hierarchy are distinguished. Four levels of morphology can be identified: chain characteristic
(primary level), crystal unit-cell (secondary level), lamellae structure (tertiary level), and
crystal aggregates or super-molecular structure (quaternary level).
A wide range of material properties are achieved depending on the chain
characteristics, type of poly